The Applicant has developed a range of Memjet® inkjet printers as described in, for example, WO2011/143700, WO2011/143699 and WO2009/089567, the contents of which are herein incorporated by reference. Memjet® printers employ a stationary pagewidth printhead offering the advantages of high-speed printing and noise reduction compared to conventional scanning inkjet printers.
To date, the commercially-available range of Memjet® printers provide simplex (i.e. single-sided) printing. Typically, paper is fed from a paper tray, around a C-chute, past the printhead, and delivered to an output tray positioned above the paper tray. The C-chute enables the output tray to be positioned above the paper tray, which reduces the overall footprint of the printer. It would be desirable to provide high-speed duplexed printers based on the Memjet® technology.
One conventional approach to duplexed inkjet printing is described in U.S. Pat. No. 6,018,640. In this type of duplexer, paper is fed past the printhead which prints onto a first side of the paper and then stops. Once the paper has stopped, it is reversed back past the printhead and around a duplexing unit, which may be a removable module of the printer. The duplexing unit typically feeds the paper around a drum such that an opposite second side of the paper is presented in its next pass of the printhead. Notably, this type of conventional duplexer feeds paper past the printhead from the same side of the printhead when printing the first and second sides.
A disadvantage of conventional duplexers, such as the duplexer described in U.S. Pat. No. 6,018,640, is that duplex-printed pages are inevitably printed at slower speeds (typically about half the speed) of simplex-printed pages. Furthermore, the duplexer has a complex media feed path which may result in paper jams. Moreover, the duplexing unit requires drive rollers that operate in two directions and is relatively noisy.
Other approaches to duplexed printing require two printheads. For example, Silverbrook's WO00/65679 describes a duplex printer having a pair of opposed pagewidth printheads. This increases the cost of the printer and, moreover, requires complex printhead maintenance systems. Alternatively, Silverbrook's WO2011/020152 describes a duplex web printer having a serpentine media feed path and two printheads positioned along the serpentine path. This arrangement has a relatively large footprint and is generally unsuitable for office printing.
It would be desirable to provide an inkjet printer, which provides duplexing with little or no speed reduction compared to simplex printing; does not require two printheads; has a smooth operation that is not prone to paper jams; and does not require complex or noisy feed mechanisms.